From a14aeb27bbfebca0f2faed3cc5826f10a9ac2956 Mon Sep 17 00:00:00 2001
From: Emil Sjolander <emilsj@fb.com>
Date: Fri, 17 Mar 2017 09:07:24 -0700
Subject: [PATCH] Avoid transfering cached layout information to java

Summary: Don't transfer layout outputs to java if the layout was cached as this means that it has already been transfered

Reviewed By: astreet

Differential Revision: D4716024

fbshipit-source-id: c30763a6fc7426d653c7a6ca129615cddb4140e9
---
 java/jni/YGJNI.cpp |  6 ++++++
 yoga/Yoga.c        | 13 +++++++++++++
 yoga/Yoga.h        |  2 ++
 3 files changed, 21 insertions(+)

diff --git a/java/jni/YGJNI.cpp b/java/jni/YGJNI.cpp
index 72e704c8..c0b0dd49 100644
--- a/java/jni/YGJNI.cpp
+++ b/java/jni/YGJNI.cpp
@@ -24,6 +24,12 @@ static void YGTransferLayoutDirection(YGNodeRef node, alias_ref<jobject> javaNod
 }
 
 static void YGTransferLayoutOutputsRecursive(YGNodeRef root) {
+  // If the node is using a cached layout it means we have already
+  // transfered it to java.
+  if (YGNodeIsUsingCachedLayout(root)) {
+    return;
+  }
+
   if (auto obj = YGNodeJobject(root)->lockLocal()) {
     static auto widthField = obj->getClass()->getField<jfloat>("mWidth");
     static auto heightField = obj->getClass()->getField<jfloat>("mHeight");
diff --git a/yoga/Yoga.c b/yoga/Yoga.c
index 65a3ba46..1b3961c9 100644
--- a/yoga/Yoga.c
+++ b/yoga/Yoga.c
@@ -459,6 +459,18 @@ void YGNodeCopyStyle(const YGNodeRef dstNode, const YGNodeRef srcNode) {
   }
 }
 
+static int YGNodeRootGenerationCount(const YGNodeRef node) {
+  if (node->parent) {
+    return YGNodeRootGenerationCount(node->parent);
+  } else {
+    return node->layout.generationCount;
+  }
+}
+
+bool YGNodeIsUsingCachedLayout(const YGNodeRef node) {
+  return node->layout.generationCount != YGNodeRootGenerationCount(node);
+}
+
 static inline float YGResolveFlexGrow(const YGNodeRef node) {
   if (!YGFloatIsUndefined(node->style.flexGrow)) {
     return node->style.flexGrow;
@@ -1811,6 +1823,7 @@ static void YGZeroOutLayoutRecursivly(const YGNodeRef node) {
   node->layout.cachedLayout.widthMeasureMode = YGMeasureModeExactly;
   node->layout.cachedLayout.computedWidth = 0;
   node->layout.cachedLayout.computedHeight = 0;
+  node->layout.generationCount = gCurrentGenerationCount;
   const uint32_t childCount = YGNodeGetChildCount(node);
   for (uint32_t i = 0; i < childCount; i++) {
     const YGNodeRef child = YGNodeListGet(node->children, i);
diff --git a/yoga/Yoga.h b/yoga/Yoga.h
index d5c5258a..054b5dc5 100644
--- a/yoga/Yoga.h
+++ b/yoga/Yoga.h
@@ -218,6 +218,8 @@ YG_NODE_LAYOUT_EDGE_PROPERTY(float, Margin);
 YG_NODE_LAYOUT_EDGE_PROPERTY(float, Border);
 YG_NODE_LAYOUT_EDGE_PROPERTY(float, Padding);
 
+bool YGNodeIsUsingCachedLayout(const YGNodeRef node);
+
 WIN_EXPORT void YGSetLogger(YGLogger logger);
 WIN_EXPORT void YGLog(YGLogLevel level, const char *message, ...);